This invention provides an actuator well-suited for use as a Stop Action Magnet, or SAM, which may be a component of a musical instrument, especially of an organ console. In addition to claviers for accessing notes of various musical pitches at the will of the organist, an organ also usually comprises so-called stops that control plural groups, called ranks, of pipes (or of sampled or synthesized sounds) whereby many musical timbres may be selected. Small organs may comprise but a few stops, but large organs may be equipped with several tens, or even hundreds of stops. For small organs, manual stop-controls often suffice. For large organs, however, it is necessary to provide means for the organist to preset chosen stop combinations prior to a performance, subsequently to be accessed during the performance using preset buttons, called pistons. For this purpose, large organs often include a memory with presetting and access means, called a combination action. When the organist pushes a piston, pre-selected stops are electrically (sometimes pneumatically) quickly activated or deactivated as if they had been simultaneously manually selected. The electro-mechanical device that activates or de-activates each stop responsive to the combination action, or responsive to manual operation, is called a SAM.
A primal prior-art “Reisner C3” SAM is offered as part no. 5566.19 by Organ Supply Industries of Erie, Pa. Subsequent improvements to early prior-art SAM designs are taught in U.S. Pat. No. 3,832,658, U.S. Pat. No. 4,726,277, FIGS. 7&8, and U.S. Pat. No. 4,851,800, FIGS. 7, 8, and 10. These prior-art SAM's are sector-rotating designs comprising two solenoidal coils for rotor operation.
Prior-art sector-rotating SAM's comprise either a spring, or two or more permanent magnets, with at least one affixed to their rotors, to provide the toggling action required by organists. Some prior-art SAM's, for example those offered by Syndyne Corp. of Vancouver, Wash., are supplied with models having different toggle forces.
Most prior-art sector-rotating SAM's are supplied with plural rotor angle options to accommodate various organ console requirements. This plurality necessitates documentation, production, and stocking of rotors having various bend angles.
Because it is desirable for all the stop tabs (SAM handles) in a row of SAM's to rest at uniform positions, both when de-activated (up) and also when activated (down), most sector-rotating SAM's are fitted with leveling adjustments to unify their toggled positions. On the Reisner C3 SAM these adjustments are on the top and bottom of the SAM. On the SAM of U.S. Pat. No. 3,832,658 offered as part #SAM by Syndyne and in that of U.S. Pat. No. 4,726,277 offered by Peterson Electro-Musical Products, Inc., these adjustments are located on one side. Installed SAM's are often lie in closely spaced rows. The space below the lowest row of SAM'S is often occupied by the tails of the upper clavier keys. Thus, once many prior-art SAM's are installed, the only adjustment likely to be accessible is the top adjustment of a top-row Reisner SAM. It is usually inconvenient to adjust an installed prior-art SAM. For this reason, organ technicians usually adjust SAM's sequentially as they are installed rather than iteratively to dismount, adjust, and remount each SAM to level it.
The Peterson PowerTab™ literature cites its “exclusive, patented Tip Polarization” as an efficiency improvement, illustrating the importance of efficient operation. Notwithstanding this citation, prior-art SAM's usually require about three watts of instantaneous power to toggle. This large instantaneous power demand often causes prior-art SAM's to fail to operate if the supply voltage becomes loaded down. This problem often occurs when a so-called “general cancel” piston is pushed, requiring simultaneous de-activation of many SAM's. Prior-art SAM's usually utilize needle-bearing pivots, through which and around which their magnetic circuits must close. The pivots of prior-art SAMS's usually offer substantial magnetic reluctance, causing inefficiency. The needle-bearing pivots of many prior-art SAM's are prone to bearing failure after a few hundred thousand operations, necessitating inconvenient replacement.
It is not unusual for prior-art SAM's to interfere with their own switches or those of adjacent SAM's, and sometimes the operation of other parts of the instrument, to the extent that at least one instance of disruption of an organ concert due to such interference has been recorded.
Whilst it is desirable that SAM's operate silently, the deceleration of the large rotor mass of two-coil SAM's militates against this desirable characteristic.
Also taught by Peterson in U.S. Pat. No. 4,726,277, FIG. 1, is a SAM of the “draw-knob” variety preferred for classical organs. It has a single-coil like the present invention, but is very different, providing rectilinear motion and being copiously endowed with linkages. Apparently such single-coil SAM's have proven problematic in the prior-art, as Peterson's present draw-knob offering is an adapted two-coil sector-rotating device.